Method of preparing dry, concentrated salts of ascorbate 2-polyphosphate

Abstract

A method of preparing dried, concentrated ascorbate 2-polyphosphate salts is provided wherein a starting aqueous solution containing the desired 2-polyphosphate species (as well as contaminating inorganic phosphates) as sodium and potassium salts is subjected to a sequential precipitation technique to first remove the contaminants, followed by recovery of the desired species. In preferred practice, the inital starting solution is first supplemented with calcium chloride and sufficient calcium hydroxide to adjust the pH from about 6-8, thereby causing precipitation of the inorganic contaminants. At this point the ascorbate 2-polyposphate species are recovered from the supernatant and dried. The latter preferably involves washing the precipitated organophosphate salts with an aqueous organic solvent, concentration, addition of a non-solvent such as ethanol to induce precipitation, and subsequent drying. The resulting product is a concentrated salt form of ascorbate 2-polyphosphate that is a free-flowing, dried powder which can be readily handled, stored and used as an active vitamin C supplement in food or pharmacological systems.

We claim: 
     
       1. A method of preparing dried, concentrated ascorbate 2-polyphosphate salts, comprising the steps of: providing a quantity of ascorbate 2-polyphosphate species and inorganic phosphate contaminants in aqueous solution;   adding a member selected from the group consisting of calcium chloride and magnesium chloride to said solution, with the concentration of said contaminants in said solution being sufficiently small to prevent formation of a gel, with the pH of the solution being at a level of below 10;   precipitating at least a portion of said contaminants as the calcium or magnesium salts thereof, with the ascorbate 2-polyphosphate species from said reaction mixture remaining in the supernatant; and   recovering said ascorbate 2-polyphosphate species from said supernatant as a dried product.   
     
     
       2. The method of claim 1, said contaminants being present in said solution at a level of no more than about 1.5% by weight calculated as phosphorus. 
     
     
       3. The method of claim 2, said contaminants being present in said solution at a level of no more than about 1.0% by weight. 
     
     
       4. The method of claim 3, said contaminants being present in said solution at a level of no more than about 0.14% by weight. 
     
     
       5. The method of claim 1, wherein calcium chloride is added to said solution, and base is added to the solution to adjust the pH thereof. 
     
     
       6. The method of claim 1, including the step of adjusting the temperature of said solution after addition of said member to a level of from about 5°-35° C. 
     
     
       7. The method of claim 6, said level being from about 10°-25° C. 
     
     
       8. The method of claim 1, the pH of said solution being at a level of from about 6-8. 
     
     
       9. The method of claim 1, the molar ratio of ascorbate 2-polyphosphate ester to calcium or magnesium ion in said solution being from about 1:2.5 to 1:4. 
     
     
       10. The method of claim 9, said ratio being about 1:3.5. 
     
     
       11. The method of claim 1, said recovering step comprising the steps of: concentrating said supernatant;   adding to said concentrated supernatant a quantity of a non-solvent for said ascorbate 2-polyphosphate species which is miscible in water, and causing said species to precipitate; and   drying said precipitated ascorbate 2-polyphosphate species.   
     
     
       12. The method of claim 11, including the step of washing said precipitate to remove chloride salts therefrom, prior to said drying step. 
     
     
       13. The method of claim 11, said non-solvent being selected from the group consisting of methanol, ethanol, tetrahydrofuran, dioxane and acetone. 
     
     
       14. The method of claim 13, said non-solvent being ethanol, and being added in a volume substantially equal to that of said concentrated supernatant. 
     
     
       15. The method of claim 12, said washing step comprising contacting said precipitate with a mixture of water and ethanol. 
     
     
       16. The method of claim 15, said water-ethanol mixture being about a 1:1 v/v mixture.